title: Folic acid reverses nitric oxide synthase uncoupling and prevents cardiac dysfunction in insulin resistance: role of Ca2+/calmodulin-activated protein kinase II.
abstract: Nitric oxide synthase (NOS) may be uncoupled to produce superoxide rather than nitric oxide (NO) under pathological conditions such as diabetes mellitus and insulin resistance, leading to cardiac contractile anomalies. Nonetheless, the role of NOS uncoupling in insulin resistance-induced cardiac dysfunction remains elusive. Given that folic acid may produce beneficial effects for cardiac insufficiency partially through its NOS recoupling capacity, this study was designed to evaluate the effect of folic acid on insulin resistance-induced cardiac contractile dysfunction in a sucrose-induced insulin resistance model. Mice were fed a sucrose or starch diet for 8 weeks before administration of folic acid in drinking water for an additional 4 weeks. Cardiomyocyte contractile and Ca(2+) transient properties were evaluated and myocardial function was assessed using echocardiography. Our results revealed whole body insulin resistance after sucrose feeding associated with diminished NO production, elevated peroxynitrite (ONOO(-)) levels, and impaired echocardiographic and cardiomyocyte function along with a leaky ryanodine receptor (RYR) and intracellular Ca(2+) handling derangement. Western blot analysis showed that insulin resistance significantly promoted Ca(2+)/calmodulin-dependent protein kinase II (CaMKII) phosphorylation, which might be responsible for the leaky RYR and cardiac mechanical dysfunction. NOS recoupling using folic acid reversed insulin resistance-induced changes in NO and ONOO(-), CaMKII phosphorylation, and cardiac mechanical abnormalities. Taken together, these data demonstrated that treatment with folic acid may reverse cardiac contractile and intracellular Ca(2+) anomalies through ablation of CaMKII phosphorylation and RYR Ca(2+) leak.
authors.affiliation: Center for Cardiovascular Research and Alternative Medicine, University of Wyoming, Laramie, WY 82071, USA.
authors.forename: Nathan D
authors.initials: ND
authors.lastname: Roe
authors.affiliation: Center for Cardiovascular Research and Alternative Medicine, University of Wyoming, Laramie, WY 82071, USA; Department of Clinical Immunology, Xijing Hospital, Fourth Military Medical University, 710032 Xi'an, China.
authors.forename: Emily Y
authors.initials: EY
authors.lastname: He
authors.affiliation: Department of Clinical Immunology, Xijing Hospital, Fourth Military Medical University, 710032 Xi'an, China.
authors.forename: Zhenbiao
authors.initials: Z
authors.lastname: Wu
authors.affiliation: Center for Cardiovascular Research and Alternative Medicine, University of Wyoming, Laramie, WY 82071, USA. Electronic address: jren@uwyo.edu.
authors.forename: Jun
authors.initials: J
authors.lastname: Ren
mesh_terms: D000818:Animals; D015153:Blotting, Western; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2 / Q000378:metabolism*; D004195:Disease Models, Animal; D005492:Folic Acid / Q000494:pharmacology*; D007333:Insulin Resistance / Q000502:physiology*; D051379:Mice; D009200:Myocardial Contraction / Q000187:drug effects; D009206:Myocardium / Q000378:metabolism; D032383:Myocytes, Cardiac / Q000187:drug effects / Q000378:metabolism; D019001:Nitric Oxide Synthase / Q000378:metabolism*; D019837:Ryanodine Receptor Calcium Release Channel / Q000187:drug effects / Q000378:metabolism; D014803:Vitamin B Complex / Q000494:pharmacology*
chemical_list: D019837:Ryanodine Receptor Calcium Release Channel; D014803:Vitamin B Complex; D005492:Folic Acid; D019001:Nitric Oxide Synthase; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2
keywords: CaMKII; Cardiac function; Folic acid; Free radicals; Insulin resistance; Intracellular Ca(2+)